For the case where the interpreter is compiled out or when the prog is jited it is completely unnecessary to set the BPF insn pages as read-only. In fact, on frequent churn of BPF programs, it could lead to performance degradation of the system over time since it would break the direct map down to 4k pages when calling set_memory_ro() for the insn buffer on x86-64 / arm64 and there is no reverse operation. Thus, avoid breaking up large pages for data maps, and only limit this to the module range used by the JIT where it is necessary to set the image read-only and executable.
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| @@ -776,8 +776,12 @@ bpf_ctx_narrow_access_offset(u32 off, u32 size, u32 size_default) · 775 unmodified lines | ||
| 776 | 776 | |
| 777 | 777 | static inline void bpf_prog_lock_ro(struct bpf_prog *fp) |
| 778 | 778 | { |
| 779 | − set_vm_flush_reset_perms(fp); | |
| 780 | − set_memory_ro((unsigned long)fp, fp->pages); | |
| 779 | +#ifndef CONFIG_BPF_JIT_ALWAYS_ON | |
| 780 | + if (!fp->jited) { | |
| 781 | + set_vm_flush_reset_perms(fp); | |
| 782 | + set_memory_ro((unsigned long)fp, fp->pages); | |
| 783 | + } | |
| 784 | +#endif | |
| 781 | 785 | } |
| 782 | 786 | |
| 783 | 787 | static inline void bpf_jit_binary_lock_ro(struct bpf_binary_header *hdr) |